Soap impregnated resilient polyurethane foams

ABSTRACT

FLEXIBLE POLYURETHAANE SPONGS, HAVING A DDRY BLAND SOAP INTEGRALLY INCORPORATED THEREIN, ARE PROVIDED BY FORMING AND FOAMING A MIXTURE COMPRISING A POLYESTER WITH A HYDROXYL NUMBER OF 40 TO 80, A MOLECULAR WEIGHT OF 2,000 TO 6,000 AND A CARBOXY NUMBER OF LESS THAN 1.5; AN AROMATIC DIISOCYANATE; WATER; A BASIC CATALYST; AND FINELY DIVIDED AND INTIMATELY MIXED BLAND SOAP WITH OR WITHOUT AN EFFECTIVE AMOUNT OF A GERMICIDE IN AN AMOUNT EQUAL TO 25 TO 110% OF THE COMBINED WEIGHT OF THE POLYESTER AND THE DIISOCYANATE TO THEREBY FORM A SPONGE HAVING FROM 60 TO 100 PORES PER INCH AND THE SOAP EVENLY DISTRIBUTED THERETHROUGH, IN A FINELY SUBDIVIDED STATE.

United States Patent US. Cl. 252-91 1 Claim ABSTRACT OF THE DISCLOSUREFlexible polyurethane sponges, having a dry bland soap integrallyincorporated therein, are provided by forming and foaming a mixturecomprising a polyester with a hydroxyl number of 40 to 80, a molecularweight of 2,000 to 6,000 and a carboxy number of less than 1.5; anaromatic diisocyanate; water; a basic catalyst; and finely divided andintimately mixed bland soap with or without an elfective amount of agermicide in an amount equal to 25 to 110% of the combined weight of thepolyester and the diisocyanate to thereby form a sponge having from 60to 100 pores per inch and the soap evenly distributed therethrough, in afinely subdivided state.

CROSS-REFERENCES This application is a continuation-in-part of Ser. No.879,564, filed Nov. 24, 1969, now abandoned in favor hereof.

FIELD OF INVENTION This invention relates to foamed polyurethaneimpregnated with a dry bland soap and to methods of preparing the same.It relates further to surgical scrub sponges and the new means ofobtaining the same.

BACKGROUND OF INVENTION The ever-widening demand for convenienceproducts, coupled with technological advances in the plastics field andin the manufacture of reasonably durable and economical sponges, has ledto the commercial availability of disposable sponges impregnated withfunctional impregnants. These sponges function both as sponges and asthe source for the cleansing agent which cleansing agent would otherwisehave been obtained from a separate source, such as a container or a cakeof soap. The user is thus required to bring only an impregnated sponge,and not both a sponge and the active agent, to the job. The convenienceof these impregnated sponges is an important enough reason for theircommercial sale, but there are other major reasons.

The problem of eliminating bacteria and other microorganisms from theskin of a surgeons hands or the hands of a sterile nurse is a veryserious one. It is standard hospital practice for operating roompersonnel to scrub their hands and forearms intensively before puttingon sterile rubber gloves. Traditionally, the scrub has been with a scrubbrush and an anti-bacterial soap, the most common of which is onecontaining 2,2'-dihydroXy-3,5,6- 3',5',6'-hexachlorodiphenylmethane,often called hexa chlorophene. Other germicidal agents such as theiodophors have been used to great advantage in surgical scrubs. Whilethe germicidal agents are quite effective, there is a serious problem ofcontamination because the soap dispensers cannot be maintained sterileeven though the dispensers are cleaned and autoclaved once a day, whichis the procedure in the best hospitals. By the use of sterile wrappeddisposable sponges containing the germicidal cleansing agent, theproblem of cross-contamination from the soap dispenser is completelyavoided. Thus, in

3,810,841 Patented May 14, 1974 addition to the convenience which apre-packaged germicide-impregnated disposable sponge provides, there isalso the advantage of the elimination of the problem ofcrosscontamination from the otherwise necessary soap dispenser.

There are available at the present time sponges which are impregnatedwith materials such as detergents, germicides and/or soaps which areprepared by a wide variety of methods. The most usual method forimpregnating the sponge is to dissolve and/ or disperse the selectedimpregnant in a liquid medium, most usually water, and thereafter soakthe sponge in the solution or dispersion. The liquid is then evaporatedfrom the sponge to leave the impregnant deposited throughout the sponge.

Another method of adding a powdered cleansing agent to the sponge isshown in US. Pat. 3,619,843, Richter and Messer, Nov. 16, 1971, SpongesWith Dry Impregnants." Here spikes and gas flow methods are used.

Sponge materials which are most widely used are synthetic in origin.Natural sponges are not in sufficient supply to fill all the modern-dayneeds for sponges. Moreover, natural sponges cannot be manufactured tohave desired degrees of porosity, texture and uniformity required inmodern-day applications. Commonly, synthetic sponges are prepared fromregenerated cellulose or expanded poly urethanes. Other expandedpolymers such as polyethylene, polyacrylate and polyvinyl acetate, havealso been used for sponge applications.

Since the liquid or dry impregnating method has severe limitations, itis highly desirable to have a process whereby sponges are impregnatedwithout the need to use liquid dispersing media for the purpose ofcarrying the impregnant into the sponge structure or adding a powder tothe foamed sponge.

It is one of the objects of the present invention to provide a methodwhereby sponges can be impregnated without the need of dissolving ordispersing the impregnant in large quantities of water.

It is a further object of the present invention to provide impregnatedsponges which can be stored for long periods of time withoutdeterioration of either the sponge material or the cleansing agent. Itis a still further object of the present invention to provide means forimpregnating a sponge material with a dry cleansing agent whereby thecleansing agent is evenly distributed throughout the sponge and isretained therein without loss due to leakage of the impregnant from thecellular structure of the sponge.

Still more particularly, it is an object of the present invention toprovide a polyurethane surgical scrub sponge which is capable of beingstored for long periods of time without deterioration of either thecleansing agent or the sponge material.

Further objects will be apparent from the ensuing description of thisinvention.

THE PRESENT INVENTION The present invention accomplishes these and otherobjects in a surprisingly simple and eflicient manner. In accordancewith this invention polyurethane foams having a dry bland soap powderintegrally and internally incorporated therein are easily andefficiently made. The said soap intimately dispersed in the polyesterresin which eventually is reacted with diisocyanate to produce thepolyurethane foam. As the polymer-forming materials in the reactionmixture react with each other the result is the production of spongematerial and the distribution of the said soap therein. Thus, by thepresent invention one obtains an impregnated sponge with little moredifficulty than is involved in obtaining an unimpregnated sponge as canbe understood from the fact that the steps of sponge formation andcleansing agent incorporation are simultaneously accomplished. Thepolyurethane sponges of the present invention are completely distinctfrom sponges prepared by the after-impregnation of sponge material.

They are also distinguished from polyurethane sponges in which achemically combined portion of the polyurethane molecule functions as asurfactant. The sponges of the present invention contain largequantities of the said soap cleansing agent (at least 25 weight percentbased on the weight of the polyurethane itself). The said soap is notchemically combined as part of the polyurethane molecule, but is anintegral part of the physical structure of the sponge and not merelyoccluded within the open cells of the sponge structure.

The type of poyurethanes which can be used for the sponges of the.present invention, the process by which they can be made, the variety ofcleansing agents which can be employed and the character of theimpregnated sponges provided by the present invention are described ingreater detail below.

Polyurethane foams In order to achieve the primary object of the presentinvention which is to provide sponges with a high proportion ofcleansing agent it is necessary to choose as the foam-producingmaterials those having a capacity to form cellular bodies in thepresence of large quantities of materials not entering into thefoam-producing reaction. In some instances the polyurethane formingmaterials are incapable of efficiently forming cellular bodies in thepresence of high quantities of the cleansing agent. In other instancesthe distribution of the cleansing agent into the foam-producing mixtureresults in such an increase in viscosity of the mixture that the mixtureis practically unworkable in conventional processing equipment. Thus,the choice of the foam-forming materials must take into account theunusually high loading factor imposed upon it by the presence of up tonearly equal weights of a cleansing agent.

Polyurethane foams are formed by the reaction of a dihydroxy compoundand a diisocyanate in the presence of a basic catalyst and water.Generally, the reaction is carried out stepwise. A dihydroxy compound isreacted with an equivalent quantity of a diisocyanate to give a reactionproduct which is a mixture of polymeric molecules having both hydroxyand isocyanto terminal groups. The polymeric material is then reactedwith excess diisocyanate in the presence of a basic catalyst and water.The latter reaction leads to the formation of the desired polyurethanemolecules and also, by reaction with water, to the generation of thefoam-producing gas (i.e. carbon dioxide).

These reactions are illustrated by the following equa tions:

In the foregoing equations R is the radical of a polyester and R is analiphatic or aromatic radical corresponding to the diisocyanate used asstating material. The same reactions have been employed prior to thepresent invention to prepare foamed polyurethanes, the distinction inthe present invention being in the polyesters used in the reaction ofEquation 1. Those which are useful in the present invention should havean hydroxyl value in the range of 40 to 80, preferably 50-52, an acidnumber of less than 2.0, preferably below 1.5 and they should be thereaction product of a dibasic acid free of ethylenic unsaturation withan excess of at least one polyhydric alcohol. The polyhydric componentis normally comprised of a mixture of a major portion of glycol and atrihydric alcohol. Suitable glycols are alkylene glycols in which thealkyl moiety has 2-4 carbons such as ethylene glycol, propylene glycol,trimethylene glycol, tetramethylene glycol, 1,3-butylene glycol,diethylene glycol, dipropylene glycol, polyethylene glycol and the like.Suitable trihydric alcohols are glycerol and trimethylolpropane.

Particularly suitable polyurethanes are obtained from polyesters havinga molecular weight of 2,500 to 2,800 derived from an aliphatic dibasiccarboxylic acid of 4 to 6 carbon atoms and a glycol of 2 to 4 carbonatoms. Reaction of a polyester of this type, e.g., poly(ethyleneadipate) or poly(butylene adipate) with an aromatic diisocyanate such astoluene diisocyanate of methylene bis (4-phenylisocyan ate) The presentinvention contemplates the use of laminated sponges of polyester-basedpolyurethanes, such as those having a relatively thick central layer offine pore material covered on either side by a thin layer of relativelycoarse sponge material. The thicker layer, having at least about 60pores to the inch acts as a reservoir for the cleansing agent. Thecoarse outer layers, one layer optionally being considerably coarserthan the other, have generally 1020 pores per inch. =If layers ofdifferent coarseness are used, one layer can have about 10 pores perinch and the other may have about 20 pores per inch. The coarser layeris useful for removing greater amounts of dirt and the less coarsematerial is useful for scrubbing skin surfaces, where the surfaces aredelicate or less heavily soiled. The coarse layers may be formed fromsponge material which is nonreticulated or has a lower degree ofreticulation. One layer needs to be reticulated to provide a passage forwater into the central part of the sponge and for egress of the waterand the cleansing agent. The fine pore central portion of the sponge hasopen pores to thereby permit contact between the cleansing agent and thewater used in connection with the cleaning operation.

Process for preparing impregnated sponges In general the process of thepresent invention involves the formation of a mixture comprising thepolyurethaneforming materials and the cleansing agent. The mixture uponbeing subjected to conditions which lead to the formation of thepolyurethane foam yields in one step an impregnated foam material. Sincethe impregnated sponges as provided by the persent invention containlarge amounts of the cleansing agent it is critical that the foamformingmaterial possess the proper viscosity whereby even in admixture with thefunctional additive it is not so viscous as to be unworkable. Moreover,the foam-forming materials must be capable of foaming in the presence oflarge amounts of inert materials.

In general, the process of the present invention involves bringing amixture of a hydroxy terminated polyester and a surfactant into reactivecontact with a diisocyanate, water and a catalyst. Thus the surfactantshould be added to the polyester component before it is mixed with theother reactants. It is important that the materials which are to be usedin forming the polyurethane foam are intimately blended prior tocommencement of the foam-forming reaction by heavy shear, such as in a 3roller paint mill or mortar and pestle. The precise means of blendingmaterials will be determined by the physical state of the impregnatedmaterial. Thus, where the impregnant is a liquid which will not increasethe viscosity of the foam producing materials it can be admixed with aviscous polyester component prior to addition of the other components.When the impregnant is a solid material which may increase theviscosity, it is better practice to add the impregnant to the lessviscous polyester resin so that it does not interfere with the properblending of all S the other materials of the foam-producing reactionmixture.

The reaction between the dissocyanate and the polyester is catalyzed bybasic materials such as N-methyl-morpholine, triethylamine,dimethylethanolamine, N-(Z-hydroxypropyl)dimethylmorpholine ordimethylformamide.

The water which enters the foaming reaction may be supplied through theaddition of water or a water-releasing reagent such as hydrated salt,e.g., magnesium sulfate hepta-hydrate, to the reaction mixture.

In addition to the above mentioned essential components of thefoam-producing reaction mixture, there may be present other materialssuch as emulsifiers and dispersants to aid in homogeneously blending thematerials in the reaction mixture whereby the polyurethane product has acellular structure of desirable physical characteristics and thecleansing agent is evenly incorporated therethrough.

A foam-producing formulation which is satisfactory for the objectives ofthe present invention will contain polyester, a suitable diisocyanate, awater releasing reagent a catalyst, the cleansing agent and, optionally,an emulsifier. The cleansing agent should constitute at least 25% byweight of the combination of polyester and the diisocyanate. Preferably,the cleansing agent will be present in an amount equal to about 90 toabout 110% of the weight of the combination of these materials, formaximizing sudsing duration.

The foam-producing reactions proceed with the formation of gas forfoaming the mixture. Advantageously, the reaction proceeds at roomtemperature. Sometimes it is desirable to control the rate of reactionby chilling; but it can also be promoted by the application of mildheat. The reaction is optionally conducted in a mold so that as themixture expands, it is formed into the desired shape. From the reactionexotherm, reaction temperatures in large masses reach the range of100-200" C.; foaming is generally completed in under two hours, afterwhich time the foam can then be removed from the mold and used asdesired. An alternative preferred method is to cast the reaction mixtureonto a moving belt directly from the mixing head. The mixturedistributes itself across the width of the belt and expands as the gasis formed. The resultant foam has a noncellular surface covering whenthe foaming takes place in the open atmosphere, which surface is usuallydiscarded. The sponge produced is cut to size and shape, by conventionalmethods. In small laboratory sized batches, an oven can be used tosimulate similar curing agents.

Impregnating materials The present invention contemplates thepreparation of polyurethane foams impregnated with any of a wide varietyof cleansing agents. The impregnant should be chemically inert to thesponge and it should not interfere with the reaction required to producethe foam. The sponges thus may have cleansing agents and other agents(e.g., abrasives) or germicides which it may be desired to use incombination with sponges.

The abrasives can be such materials as pumice, kaolin, chromium oxide,iron oxide and the like. Detergents which can be dispersed in thepolyurethane foam including alkylaryl sulfonates, the fatty acidsulfates, and the polyalkylene oxides in combination with a fatty acidsoap to provide lathering action.

The present invention is particularly useful for the preparation ofpolyurethane sponges impregnated with a germicidal cleansing agent foreither home or hospital use. Such preferred germicidally active spongescontain a bland neutral soap, preferably a high grade toilet soap; adetergent which may be of the nonionic, cationic, or anionic type; andoptionally a sequestering agent such as tetrasodium ethylene-diaminetetraacetic acid. The combination of the detergent, the soap and thesequestering agent provides excellent cleansing action without being tooharsh on the skin as would be the case if only detergent were used. Inaddition, preferred germicidal compositions should contain a dryemollient to help replace skin oil removed during the scrubbing processand help solubilize the germicidal agent. Among such dry emollients areethoxylated lanolin and high molecular weight polyethylene glycols.

A bland neutral soap refers to a reaction product of a caustic such assodium hydroxide or sodium carbonate and a fatty acid, or mixture offatty acids, such as in palm oil, or olive oil or tallow, containingpalmitic acid, stearic acid, lauric acid etc. in which the proportionsare such that essentially all of the caustic is reacted with a fattyacid, so that no free alkali remains, and which has a pH of about 7 toabout 11, when dissolved in water, depending on the soap concentrationand. the quality of water. In distilled water, a 1% solution typicallyhas a pH of 10.1 at 25 C. for a typical such soap (Dial soap powder). Intap water, the pH measured 7.4 for tap water at Pearl River, NY. The pHvaries depending on the amount of CO and other materials in the tapwater-and can vary from day to day in a given location.

An essential feature is that the dispersed particles of said soap besufliciently finely dispersed that a single particle of maximum size besmaller than the strands forming the recticular cell wall structure ofthe open pore polyurethane foam. US. Pat. 3,171,820, Volz, ReticulatedPolyurethane Foams and Process for Their Production shows methods ofpreparing open foams, in which the cell walls have open areas to allowliquids to pass through readily.

Here cleansing agent, such as the dry bland soap, which may contain abactericidal agent, is incorporated into the cell wall structure. If acleansing agent particle is large enough to be a major portion of thecross section of an interconnecting strand, the strand is weakened, anda large number of weakened strands weakens the sponge structure. A fewpercent of weakened strands is acceptable.

Here the cleansing agent particles are much smaller than the diameter ofthe interconnecting strands, and the sponge maintains strength andintegrity even if the loading is from 25 to percent of the polyurethanefoam weight.

Additionally, some of the cleansing agent particles are totally covered,which delays the release rate to further assure that the rate ofcleansing agent release is such that the sponges deliver a sudsing foamduring a 10 minute surgical scrub.

With surgical scrub sponges, the individual strands are conveniently ofa diameter in the order of 50 to 250 microns, and with cleansing agentparticles below 50 microns, and predominantly in the 5 to 20 micronsize, adequate strength is retained even after the cleansing agent isexhausted.

The dry bland soap forming the cleansing agent is dispersed in thepolyester component by high shear techniques. Such include, but are notlimited to the use of a 3-roller paint mill, on a larger scale, or amortar and pestle on a small scale. The polyester is very viscous, andrequires a powerfull high shear system, such as a 3-roller paint mill togrind and intimately admix the composition. The dry soap is best milleduntil effectively dispersed in particles smaller than about 50 micronsin maximum dimension and preferably until most of the dispersed phase isin particle size smaller than about 15 microns. Particles smaller than 5microns are acceptable but it is not necessary to grind an appreciablefraction below 5 microns, although the material may be so ground, andgives excellent results.

Germicides to provide the antimicrobial action include hexachloropheneand/or one of the germicidally active compounds known as iodophors.These iodophors are iodine complexes which are capable of liberatingiodine when in contact with water. The term is applied to any product inwhich surface active agents (such as nonyl phenoxypolyethoxyethanol) orpoly(vinyl pyrrolidone) act as carriers and solubilizing agents foriodine. An iodophor usually enhances the bacterial activity of iodineand reduces its vapor pressure and odor. Staining is almost nonexistentand wide dilution with water is possible. An example of theirpreparation is given in U.S. Pat. 2,710,- 277. Iodophors are effectiveat acid pH so that if the germicidal agent is an iodophor, an acidicmaterial may be added to the composition as a stabilizer. Among suchacidic materials are citric acid, ascorbic acid, tartaric acid,phosphoric acid, etc. Generally, if the cleansing agent contains about0.5 to 2.0% of iodine content, effective germicidal activity isobtained.

One of the most important advantages of the present invention is thatthe sponges can be impregnated with combinations of materials which aregenerally incompatible under moist conditions. Thus, for example,surgical scrub sponges prepared by the conventional liquid impregnationmethod known heretofore, could not contain a combination ofhexachlorophene and an iodophor since these materials react with eachother under moist conditions. Thus, after a short period, the twomaterials would cancel each other out and no germicidal activity wouldremain. The combination of the hexachlorophene and an iodophor is muchmore useful germicidally than either alone since hexachlorophene isgenerally active against gram-positive microorganisms and the iodophorsaregenerally active against the gram-negative microorganisms. Where bothtypes of pathogens are present, neither germicide alone is as effectiveas a combination.

Advantageously, sponges containing both hexachlorophene and an iodophorcan be prepared by this invention since the small amount of water whichis present in the polyurethane reaction mixture does not remain incontact with the germicides for a sufficiently long period to cause theinactivation of either material. It may be desirable when using amixture of hexachlorophene and an iodophor to add these materials to thereaction mixture only shortly before polymerization is initiated inorder to reduce the amount of time in which the materials are in contactwith water. At any rate, once the polymerization reaction has beencompleted the water which was necessary for the formation of the foam isno longer present and the germicidal materials can thereafter remainstable during long periods of storage.

The sponges of the present invention The process by which thepolyurethane sponges of this invention are prepared, although involvingthe incorporation of the cleansing agent into the polymerizable reactionmixture, does not result in the chemical bonding of the additive to thepolyurethane. The cleansing agents completely dispersed throughout thesponge material and very intimately associated with the cellularstructure. When a sponge product of this invention is examined by darkfield and bright field polarized light techniques it is observed thatthe additive particles are uniformly distributed throughout, andpredominantly in the particle size range of to 15 microns. Particles ofsurfactant were found on the windows and struts or strands of the spongecells. Thus the cleansing agent is present in very intimate associationin the sponge structure in a manner which is definitely distinct fromthe type of association resulting when a liquid soap or detergent isimpregnated by the conventional liquid impregnation methods. Much morecleansing agent can be held by the sponge than is the case whenconventional impregnation procedures are employed. Moreover, since theamount of impregnant which is added to the sponge is not dependent uponthe ability of a liquid impregnation medium to hold the impregnant in adispersed state, the amount of impregnant which can be incorporated intothe sponge is not dependent upon the amount which can remain stablysuspended in a liquid medium. These facts make possible the productionof sponges with very high concentrations of cleansing agent.

The sponges of the present invention after being formed are cut to sizeand wrapped either individually or in a package containing severaltogether. The wrapping need not be waterproof or have any specialquality since the contents are substantially dry. Preferably, when thesponge is to be used in hospital antiseptic procedures, the wrappingmaterial is one which prevents the penetration of microorganisms whileat the same time permitting the passage of cold sterilizing agents suchas ethylene oxide gas or is transparent to radiation when sterilizationis to be by radiation. So long as these characteristics are present theparticular composition of the wrapper is not of any particular concernto the present invention except of course that obviously it must not besomething that is either itself toxic or which is capable of adversereaction with the sponge or the impregnated functional additive.

The following examples are presented to further illustrate the presentinvention.

EXAMPLE 1 This example illustrates the preparation of a preferredantiseptic cleansing sponge in accordance with the present invention.The following compositions were prepared.

Polyester-soap mix: G. Polyester 1,000 Hexachlorophene 40 Bland soappowder 1,000

Activator mix: G. Water (DI) 35 N'-ethyl-morpholine 5 N-coco-morpholine5 /20 isomeric mixture of 2,4/ 2,6 toluene diisocyanate.

The polyester used in component (A) is the reaction product of adipicacid, ethylene glycol and glycerol with a molecular weight of 2,500; anacid number of less than 1.5; viscosity of 17,000-22,000 centipoises;Brookfield Model LVF, Spindle No. 4 (l2 r.p.m.) and a s.p. 1.18 to 1.20at 25 C.

134 g. of (A) and 46 g. of (C) were mixed thoroughly. Six g. of (B) wasadded with vigorous stirring and the reaction mixture was poured as itbegan to heat up, into a cardboard mold. It was cured at roomtemperature for 30 minutes. The product was removed from the mold, apiece was cut away and it was used for scrubbing hands. The spongesudsed copiously as soon as it was wetted and continued to do so duringa ten-minute scrub.

EXAMPLE 2 A mixture was prepared of:

Parts Polyester resin 100.0

Silicone resin 1.5 Bland neutral soap powder containing 3%hexachlorophene 25.0

these components were blended in a mortar and pestle until the soap waspredominantly in the particle size range of 4 /2 to 14 microns. A fewaggregates existed but photomicrographs show no aggregates more than 50microns in the largest dimension.

To this mixture was added 46 parts of an 80/20 isomeric mixture of2,4/2,6 toluene diisocyanate. The components were blended in a highspeed blender until uniformly mixed and thereto added 6 parts of amixture of deionized water and N-ethyl morpholine in the ratio of 35/10parts by weight. This catalyst mixture was added to the vigorouslystirred mixture and as soon as the mixture started to react, as shown byan exothermic reaction, the contents were poured into a cardboard moldand left to cure. After 30 minutes the product was sufficiently cured tobe removed from the mold and used. A section 1 inch by 2 inch by 3 inchwas cut from the molded product and used as a sponge for scrubbing thehands in accordance with surgical techniques. The sponge released sudscopiously as soon as it was wetted and continued to do so during theentire duration of a minute surgical scrub.

The polyester component was the reaction product of adipic acid ethyleneglycol, and glycerol with a molecular weight of about 2,500, an acidnumber of less than 1.5 and a viscosity of approximately 22,000centipoises measured on a Brookfield Model LVF, No. 4 spindle at 12 rpm.A commercial source of such resin is Witco Fomrez-SO.

The silicon resin is a dimethylsiloxane resin used as a liquidsurfactant to aid in pore size control. The use of the silicon resinpermits fine pore size sponges to be obtained with less intense andvigorous mixing than would otherwise be required. A more intense mixingcan be used instead of or in addition to the silicon resin dependingupon the pore size of product which is desired.

Whereas the sponge produced in this sample had a range of about 60 to100 pores per inch, the mixing speed can be controlled to modify thesponge pore size if desired.

EXAMPLE 3 The procedure set forth in Example 2 was followed except that100 parts of the bland neutral soap powder containing 3% hexachlorophenewas added to the mixture. The processing was the same and the productfound to be a soft textured adaptable sponge, which released suds ingreater quantity and for a longer time than the product of Example 2.

Copious suds were still being released after a minute scrub.

As the suds release rate bears certain of the characteristics ofexponential decay, a sharp end point to sudsing is not obtained.Products are best rated by a comparative test with a single user usingaparticular type and temperature tap water under controlled conditions.As with most other uses of soap, hard water inhibits the formation offoams. Even in tap water, as it is used for scrubbing in most hospitals,copious suds are released for at least 10 minutes of vigorous scrubbing.

EXAMPLE 4 A sudsing mixture used as the cleansing agent was prepared byblending 943 parts by weight of the sodium salt of an 85%, tallow 15%cocoanut oil soap powder to which was added 2 parts of alkylarylsulfonate, 0.7 part of glycerine and 3.0 parts of hexachlorophene.Of this mixture, 25 parts were combined with 100 parts of the polyesterresin of Example 2 and 1.5 parts of silicon resin. A large size batchwas used. The soap was intimately dispersed to predominantly less than15 microns particles size in a 3 roller paint mill. The same techniquesas pigment grinding apply. A heavy shear breaks up and disperses thecleansing agent. To the well dispersed mixture was added 46 parts of80/20 isomeric 2,4/ 2,6 toluene diisocyanate and 6 parts of the 35/ 1Odeionized water N-ethyl morpholine catalyst system. The polyestercomposition and the toluene diisocyanate were well mixed in a high speedblender prior to the addition of the catalyst, and after the addition ofthe catalyst as the mixture started to heat up, it was poured into moldsfrom which it could be cut into scrub sponge size blocks. A 30 minutecure is adequate to permit cutting and packaging, although the blocks offoam can be stored for months before being cut into the sponge blocks,if production requirements indicate. A one by two by three inch blockwas found to be a readily handlable size, althrough larger or smallercould be used by individuals having larger or smaller hands, or forother scrub purposes.

The sponges so formed gave excellent sudsing during a 10 minute surgicalscrub.

10 EXAMPLE 5 The above example was repeated using 100 parts of the samesudsing cleansing agent as in Example 4. A sponge having good texture,good body and good scrub characteristics was obtained.

The sponge was free from fragmentation during a typical 10 minute scrubby a surgeon. The additional quantity of soap gave insurance of adequatesudsing in hard water areas for prolonged periods of intense scrubbing.

EXAMPLE 6 To 100 parts of the polyester is added 1.5 parts ofdimethylsiloxane and 25 parts of a bland neutral soap powder containing3% of hexachlorophene. Additionally is added 15 parts of poly(vinylpyrrolidone) iodophor containing about 10% iodine. After the mixture isintimately blended by milling on a 3 roller paint mill until theparticle size is essentially smaller than 15 microns, the mixture hasadded thereto 46 parts of an /20 isomeric mixture of 2,4/ 2,6 toluenediisocyanate and the mixture is blended until intimately mixed, than 6parts of the 35/10 water N-ethyl morpholine catalyst are added and asreaction causes an exotherm, the mixture is poured into a mold andpermitted to foam.

This composition is particularly effective in that it has both an iodineand hedachlorophene bactericidal agent present with the iodophor actingagainst gram-negative microorganisms and the hexachlorophene againstgrampositive microorganisms.

In accordance with conventional procedures, in large scale operations,the foams may be formed on foaming machines to which two or more linesare connected with the resin-water-coupling agent and cleansing agentmixed and metered through one line and toluene diisocyanate through theother. Also foam-ing machines may be used in which the resin containingthe cleansing agent is fed through one line, the toluene diisocyanate asecond and the activator solution, water and catalyst, is meteredthrough a third line. The one shot or continuous mixing systems areadvantageously used in large scale production in which the foam iscontinuously produced on moving belts, the size and movement of the massbeing such as to accomplish the production objectives of a particularoperation. Many thousands of cubic feet a day of cleansing agentcontaining foam can be produced on a single moving belt machine.

Other formulations may be used adjusting the type and ratios of resinsand toluene diisocyanate isomers to achieve harder or softer resins.Conventional techniques are used to modify to a type desired.

For instance if the isomeric toluene diisocyanate ratio is changed from80/20 of the 2,4/2,6 isomer to a ratio of 65/35, a foam of higherdensity, and compression modulus is obtained.

The rate of stirring at the time of the catalyzation has an effect onthe size of the pores as does the use of the silicone resin.

For a strong readily handlable sponge which may be used for scrubbingand which still maintains its integrity after a 10 minute scrub, it isessential that the cleansing agent be sufficiently dispersed by highsheer techniques that the individual particles of the cleansing agent besufficiently smaller than the cell wall structure that the cell wallstructure is not unduly weakened. A few larger particles which wouldresult in the rupture of a few cell walls can be tolerated. For examplea rupture of one percent of the cell walls which would result in a onepercent weakening of the foam would be minimal. If many large particlesof cleansing agent are present, the sponge is so apt to crumble that aneffective sponge is not obtained.

Whereas a wide range of proportions in the ratio of cleansing agent inthe sponge are effective, as a surgical scrub sponge, the quantity ofcleansing agent must be such that a one by two by three inch scrubsponge releases suds 1 1 copiously for at least 10 minutes in hardwater. An unduly high ratio of cleansing agent unnecessarily adds to thecost of the sponge. About 25 to 110% based on the weight of polyurethanein the foam gives good results.

Having thus set forth the description of the present invention, theinvention itself is defined by the following claims in which all partsare by weight unless otherwise clearly indicated.

I claim:

1. The process of preparing a surgical scrub sponge which releases sudsfor at least ten minutes during a surgical scrub which comprises:

(a) forming a polyester mixture containing 100 parts of a hydroxyterminated polyester resin of a molecular weight of 2,000 to 6,000, ahydroxy number of 40 to 80 and an acid number of less than 2, adding 1.5parts silicone resin and 25 parts of a mixture of 94.3 parts of a soappowder which is the sodium salt of 85% tallow, 15% cocoanut oil, 2 partsalkyl arylsulfonate, 0.7 part glycerine, and 3 parts hexachlorophene (b)grinding in a 3 roller paint mill until the soap mixture is dispersed topredominantly less than 15 microns particle size adding 46 parts of80/20 isomeric 2,4/2,6 toluene diisocyanate and 6 parts of a 35/ 10deionized water/ N-ethyl morpholine catalyst and (d) mixing well,thereby reacting the diisocyanate, the

polyester and water under conditions such that a polyurethane and carbondioxide are concurrently formed whereby the polyurethane is caused toexpand and foam to thereby give a polyurethane sponge having uniformpore size and at least about pores per inch having the said soap evenlydispersed therethrough, in particles smaller than than 15 microns.

References Cited UNITED STATES PATENTS OTHER REFERENCES Schwartz et al.:Surface Active Agents, 1949, pp. 182.

HERBERT B. GUYNN, Primary Examiner US. Cl. X.R.

